Solar light contains rays of various wavelengths such as ultraviolet rays, visible rays, infrared rays and so on. Since the wavelength of ultraviolet ray is short and an energy thereof is high, in the prior art, the ultraviolet ray has been recovered as an electric power by a solar cell as a photovoltaic element. Also, since infrared ray in the solar light is a heat ray, it can be utilized as a heat source. For example, according to an invention taught by Japanese Patent Laid-Open No. 2001-53322, a thermoelectric element is arranged underneath a solar cell, and a thermal electric generation is carried out in addition to a photovoltaic generation by cooling a lower part of the thermoelectric element by cooling means.
Meanwhile, because solar light contains heat rays as explained above, a cooling effect is degraded if the heat rays enter in a room or in a passenger compartment of a vehicle. Therefore, according to a cabin temperature rise restricting device for a vehicle taught by Japanese Patent Laid-Open No. 2004-114900, sun beams are shielded by a light control glass and by closing a sunshade according to an outer temperature, an amount of solar radiation, or a position of the sun measured by a navigation system.
According to the invention disclosed in the above-mentioned Japanese Patent Laid-Open No. 2001-53322, cooling means has to be arranged in the system for the purpose of cooling the underside of the thermoelectric element. Therefore, and the solar light is shaded by the cooling means. This means that this system is assumed to be unsuitable for a window glass guiding a light into a room. Thus, this system has to be improved in this point.
On the other hand, the invention disclosed in Japanese Patent Laid-Open No. 2004-114900 is capable of shading or reducing solar radiation disturbing or degrading air conditioning efficiency. However, since the solar energy is shaded, the energy cannot be recovered and utilized. Thus, this system also has to be improved to utilize clean and natural energy effectively.